Parent ratings are the most widely-used measures of temperament in the literature. Many conclusions regarding child behavior and developmental outcomes (e.g., behavior problems, sibling relationships) have been based on studies utilizing such measures. However, research using twins suggests that parent ratings may exaggerate the differences between sibling temperaments. Most temperament research examines only one child per family, therefore, such effects will go undetected. The proposed project is a pilot study exploring parental perceptions of temperament in non-twin siblings. The research focuses on two questions: 1) Do parents exaggerate the temperamental differences between their siblings? 2) If so, are the previously reported relations between sibling differences in temperament and child outcome a result of parental expectations rather than actual child behavior? The sample will include 100 families with two children between the ages of 3 and 8 years. Parent ratings of temperament will be obtained for each sibling. For one-half of the families, parents will rate the temperaments of either children contemporaneously. The remaining families will have a one- month interval between the ratings of temperament assessed for a 48-hour period using mechanical motion recorders. Shyness will be assessed via behavioral observations within the laboratory. Parents' ratings of maternal differential treatment (affection and control) and positivity within the sibling relationship will be obtained. Sibling resemblance, as indexed by intraclass correlations, for parent-rated temperament will be examined. Parents perceptions of sibling differences for activity and shyness will be validated against objective measures. The association between sibling differences in temperament and outcome measures (quality of sibling relationship and differential maternal treatment) will be explored using both parent-report and objective measures of activity and shyness. This pilot study is a first step in understanding parents' perceptions of temperament in non-twin siblings. The results of this research could have significant implications for the study of temperament, not only methodologically, but substantively. For example, it is found that parents exaggerate behavioral differences between siblings, it would be important to understand how and why these perceptions are formed, whether they are enduring throughout development, and the consequences that these parental perceptions may have on children's behaviors and self perceptions.